为研究土工膜气胀及其与地下水位上升、水库蓄水及库水位骤降等影响因素的关系,研制了土工膜气胀模型试验装置,并对不同模拟工况下的土工膜位移、膜下气压、吸力、孔隙水压力以及竖向土压力的变化规律进行了试验研究.结果表明:膜下气压和孔隙水压力均随地下水位上升而增大,其大小由地下水位上升幅度决定;当地下水位与土工膜之间的非饱和区域较小时,膜下孔隙压力受库水荷载作用增加显著,在蓄水初期极易引发土工膜气胀变形,建议在膜上设置一定压重防止土工膜被顶起;膜下孔隙压力变化滞后于膜上荷载,库水位骤降时,膜下气压将大于膜上荷载,从而引起土工膜气胀破坏.%It is recognized that air expansion of geomembrane is essentially a three-phase coupled problem,which is water-air-solid in unsaturated soil,and is influenced by the rise of ground water level,storage of the reservoir and the rapid draw down of the water level in the reservoir.In this respect,a special laboratory equipment for the air expansion test of geomembrane is developed.Air expansion tests are then conducted to explore the variations of the displacement,gas pressure,suction,pore water pressure and vertical earth pressure under different working conditions.The test results show that the pore air pressure and pore water pressure are increased with the rise of the ground water level and the magnitude of the air pressure is dependent on the rising amplitude of groundwater level.It is found that the pore pressure of the soil under the geomembrane is significantly increased due to the increased water pressure during storage in the reservoir,and air expansion failure in the geomembrane is more likely to be induced at the initial storage period,especially when the unsaturated zone between the ground water level and geomembrane is small.It is therefore suggested that a certain amount of preloading could be applied over the geomembrane to prevent its expansion behaviour.As the pore pressure response below the geomembrane is usually later than the preloading above the geomembrane,pore pressure would become larger than the preloading applied during the rapid draw down of water level in the reservoir,which will lead to the air expansion failure on the geomembrane.
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